Impact of two rounds of praziquantel mass drug administration on Schistosoma mansoni infection prevalence and intensity: a comparison between community wide treatment and school based treatment in western Kenya

AbstractThis study compared the effectiveness of the community-wide treatment and school-based treatment approaches in the control of Schistosoma mansoni infections in villages with ⩾25% prevalence in western Kenya. Stool samples from first year students, 9–12year olds and adults (20–55years) were analyzed by the Kato–Katz technique for S. mansoni eggs. After two rounds of treatment, S. mansoni prevalence and intensity levels significantly declined in both treatment approaches. Prevalence comparisons between the two approaches did not show any significant differences following treatment. However, infection intensity levels in the 9–12year old school-attending pupils were significantly higher in the community-wide treatment arm than in the school-based treatment arm. Nevertheless, significant reductions in S. mansoni infection prevalence and intensity levels were achieved among school-age children regardless of the treatment approach used

Diet and hygiene practices influence morbidity in schoolchildren living in Schistosomiasis endemic areas along Lake Victoria in Kenya and Tanzania—A cross-sectional study

<div><p>Background</p><p>Since 2011, cohorts of schoolchildren in regions bordering Lake Victoria in Kenya and Tanzania have been investigated for morbidity caused by <i>Schistosoma mansoni</i> infection. Despite being neighbouring countries with similar lifestyles and ecological environments, Tanzanian schoolchildren had lower <i>S</i>. <i>mansoni</i> prevalence and intensity and they were taller and heavier, fewer were wasted and anaemic, and more were physical fit compared to their Kenyan peers. The aim of the present study was to evaluate whether diet and school-related markers of socioeconomic status (SES) could explain differences in morbidity beyond the effect of infection levels.</p><p>Methods and principal findings</p><p>Parasitological and morbidity data from surveys in 2013–2014 were compared with information on diet and school-related markers of SES collected in 2015 using questionnaires. A total of 490 schoolchildren (163 Kenyans and 327 Tanzanians) aged 9–11 years provided data. A higher proportion of Tanzanian pupils (69.4%, 95% CI: 64.3–74.5) knew where to wash hands after toilet visits compared to Kenyan pupils (48.5%, 95% CI: 40.9–56.1; <i>P</i><0.0005). Similar proportions of children in the two countries ate breakfast, lunch and dinner, but the content of the meals differed. At all three meals, a higher proportion (95% CI) of Tanzanian pupils consumed animal proteins (mostly fish proteins) compared to their Kenyan peers (35.0% (28.3–41.7) vs. 0%; <i>P</i><0.0005 at breakfast; 69.0% (63.9–74.1) vs. 43.6% (35.8–51.4); <i>P</i><0.0005 at lunch; and 67.2% (62.1–72.3) vs. 53.4% (45.8–61.0); <i>P</i> = 0.003 at dinner). Multivariable analyses investigating risk factors for important morbidity markers among individuals revealed that after controlling for schistosome and malaria infections, eating animal proteins (fish) and knowing where to wash hands after toilet visits were significant predictors for both haemoglobin levels and physical fitness (measured as VO₂ max).</p><p>Conclusions</p><p>These results suggest that the differences in morbidity may be affected by factors other than <i>S</i>. <i>mansoni</i> infection alone. Diet and hygiene practice differences were associated with health status of schoolchildren along Lake Victoria in Kenya and Tanzania.</p><p>Trial registration</p><p>Trials Registration numbers: <a href="https://clinicaltrials.gov/ct2/show/ISRCT 16755535" target="_blank">ISRCT 16755535</a> (Kenya), <a href="https://clinicaltrials.gov/ct2/show/ISRCT 95819193" target="_blank">ISRCT 95819193</a> (Tanzania).</p></div

Regression coefficients (<i>B</i>), 95% confidence intervals (95% CI) and corresponding <i>P</i> values of variable found to be significant predictors of physical fitness, VO₂ max (mL/kg/min) in children in Kenya and Tanzania in a multivariable linear regression model ^*.

<p>Regression coefficients (<i>B</i>), 95% confidence intervals (95% CI) and corresponding <i>P</i> values of variable found to be significant predictors of physical fitness, VO₂ max (mL/kg/min) in children in Kenya and Tanzania in a multivariable linear regression model ^{<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0006373#t006fn001" target="_blank">*</a>}.</p

Year 3 cross-sectional measurements of parasitological, demographic, anthropometric, haematological and physical parameters in schoolchildren in Kenya and Tanzania *.

<p>Year 3 cross-sectional measurements of parasitological, demographic, anthropometric, haematological and physical parameters in schoolchildren in Kenya and Tanzania *.</p

Summary of questionnaire results from the schoolchildren in Kenya and Tanzania.

<p>Summary of questionnaire results from the schoolchildren in Kenya and Tanzania.</p

The two-armed cohort study (arms in bold) was nested in a larger cross-sectional study.

<p>The cohort study investigated the effects of the most intense level of treatment (arm 1) and the less intense treatment strategy (arm 6) on subtle morbidity. Arm 1 represents the community-wide treatment (CWT) and arm 6 represents biannual school-based treatment. Holiday means that no PC was provided that year. Arrows indicate years where morbidity assessments were performed and the bold arrow indicates when the parasitological and morbidity data used for this study were collected. Questionnaire data was collected 1½ years (Kenya) and ½ year (Tanzania) after collection of parasitological and morbidity data.</p

Univariable association of demographic, anthropometric, parasitological (including treatment history), and diet and school-related markers of socioeconomic status with haemoglobin (Hb) level (g/L; adjusted for altitude) of the schoolchildren ^*.

<p>Univariable association of demographic, anthropometric, parasitological (including treatment history), and diet and school-related markers of socioeconomic status with haemoglobin (Hb) level (g/L; adjusted for altitude) of the schoolchildren ^{<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0006373#t003fn007" target="_blank">*</a>}.</p

The genome and transcriptome of the snail Biomphalaria sudanica s.l.: immune gene diversification and highly polymorphic genomic regions in an important African vector of Schistosoma mansoni

Abstract Background Control and elimination of schistosomiasis is an arduous task, with current strategies proving inadequate to break transmission. Exploration of genetic approaches to interrupt Schistosoma mansoni transmission, the causative agent for human intestinal schistosomiasis in sub-Saharan Africa and South America, has led to genomic research of the snail vector hosts of the genus Biomphalaria. Few complete genomic resources exist, with African Biomphalaria species being particularly underrepresented despite this being where the majority of S. mansoni infections occur. Here we generate and annotate the first genome assembly of Biomphalaria sudanica sensu lato, a species responsible for S. mansoni transmission in lake and marsh habitats of the African Rift Valley. Supported by whole-genome diversity data among five inbred lines, we describe orthologs of immune-relevant gene regions in the South American vector B. glabrata and present a bioinformatic pipeline to identify candidate novel pathogen recognition receptors (PRRs). Results De novo genome and transcriptome assembly of inbred B. sudanica originating from the shoreline of Lake Victoria (Kisumu, Kenya) resulted in a haploid genome size of ~ 944.2 Mb (6,728 fragments, N50 = 1.067 Mb), comprising 23,598 genes (BUSCO = 93.6% complete). The B. sudanica genome contains orthologues to all described immune genes/regions tied to protection against S. mansoni in B. glabrata, including the polymorphic transmembrane clusters (PTC1 and PTC2), RADres, and other loci. The B. sudanica PTC2 candidate immune genomic region contained many PRR-like genes across a much wider genomic region than has been shown in B. glabrata, as well as a large inversion between species. High levels of intra-species nucleotide diversity were seen in PTC2, as well as in regions linked to PTC1 and RADres orthologues. Immune related and putative PRR gene families were significantly over-represented in the sub-set of B. sudanica genes determined as hyperdiverse, including high extracellular diversity in transmembrane genes, which could be under pathogen-mediated balancing selection. However, no overall expansion in immunity related genes was seen in African compared to South American lineages. Conclusions The B. sudanica genome and analyses presented here will facilitate future research in vector immune defense mechanisms against pathogens. This genomic/transcriptomic resource provides necessary data for the future development of molecular snail vector control/surveillance tools, facilitating schistosome transmission interruption mechanisms in Africa